Transport parameterization of single Josephson junction charging effects and coupling energy

Josephson junctions (JJs) provide the nonlinear inductance in superconducting qubits where the qubit resonance frequency depends on the Josephson energy E_J and charging energy E_C of the junction. In the widely used transmon configuration, E_J>>E_C in order to minimize the sensitivity of the qubit to charge noise. We report here low-frequency transport measurements on single Al test JJs as well as JJs in transmons. We observe charging effects in the IV curves of junctions made with bridgeless evaporation techniques. In contrast, JJs fabricated with the Dolan bridge technique do not show charging effects. Additionally, we observe large switching currents in Dolan junctions compared to bridgeless junctions with similar characteristics, suggesting that the fabrication technique may play a role in the qubit's susceptibility to charge noise and in qubit coherence times.

*SQMS Grant 60058097

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Bulletin of the American Physical Society

2024 APS March Meeting

Monday–Friday, March 4–8, 2024; Minneapolis & Virtual

Session Q48: Superconducting Qubits: Junctions

Abstract: Q48.00009 : Transport parameterization of single Josephson junction charging effects and coupling energy*

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